1. Field of the Invention
This invention pertains generally to electrodes charged particle accelerating and storing devices and particularly to anode structures intended to be maintained at a positive potential having specific features to reduce secondary emission and sputtering phenomenon.
2. Description of the Prior Art
Many devices make use of the flow of molecular atomic or subatomic particles in a controlled ambient.
The ambient may be a vacuum or a known pressure of desired gases depending upon the function required of the particular device. The particles may be electrons or electrically charged ions or molecules.
These devices are usually associated with means for accelerating the particles such as a system of electrodes whose potentials are known.
Frequently, use is also made of magnetic fields. Whatever the nature of the particles may be they are usually in motion and so possess a kinetic energy. In some cases, in order to perform their desired function, the primary particles are caused to impinge upon a target. For instance in the case of a thermionic valve electrons emitted from a cathode are accelerated by an electric potential thus gaining kinetic energy and eventually are collected upon an anode, whereupon the kinetic energy of the electrons is at least partially transformed into other forms of energy.
In other cases the particles may deviate from their intended path and impinge upon surfaces within the device upon which they are not intended to impinge. Such is often the case in devices known as particle storage devices or accelerators such as cyclotrons, betatrons etc. Furthermore the controlled beam of particles may collide with molecules or atoms of the residual gas atmosphere of the device causing these molecules or atoms to undesirably impinge upon surfaces within the device.
When a particle impinges upon a surface several phenomena may occur depending upon the kinetic energy and nature of the particle and the surface. The kinetic energy of the particle may be transformed into vibrations of the atomic lattice constituting the impacted surface and thus manifests itself as heat. The energy of the particle may be transferred to only one or a few of the atoms of the impacted surface lattice in which case these atoms may become detached from the surface. Such detached atoms can deposit upon other surfaces within the device. This phenomenon known as sputtering is usually undesirable. The impinging particle may cause the surface to re-emit charged particles such as in the well known effect of secondary electron emission. Again such secondary emission is very often undesirable. Alternatively the particles may simply be reflected. Thus a surface which, intentionally or unintentionally is impinged upon by particles can cause undesirable effects.
It is therefore an object of the present invention to provide a particle collecting body which is substantially free from one or more of the defects of previously known particle collecting surfaces.
Another object of the present invention is to provide a particle collecting body which is substantially free from sputtering.
A further object of the present invention is to provide a particle collecting body which is substantially free from secondary electron emission.
Yet another object of the present invention is to provide an electron or charged particle device containing at least one particle collecting body which is substantially free from sputtering or secondary electron emission.
Further objects and advantages of particle collecting bodies according to the present invention will be obvious to those skilled in the art from the following detailed description thereof.